Conventionally, in an adhesive agent or sealing agent for an engine periphery or in-vehicle member of an automobile, heat resistance with which changes of rubber properties are small even after the adhesive agent or sealing agent left to stand for a long period of time under a high-temperature environment of 120° C. is required. In JP 2005-272703 A (corresponding to the specification of US 2005/215706 A) and JP 2011-252079 A, there is a disclosure that a silicone resin is suitable as the adhesive agent or sealing agent described above. However, siloxane with a low molecular weight existed in a silicone resin has a problem causing trouble in an electric contact point, and has a fear of an adverse effect when being used in electric or electronic parts. Under these circumstances, in recent years, as a material in place of the silicone resin, a composition using a (meth)acrylic polymer has been attracting attention.
For example, in JP 2006-273918 A, there is a disclosure of a composition for electric or electronic parts, which includes a (meth)acrylic polymer having a (meth)acrylic group and an initiator, but there has been a problem that the composition has high viscosity and poor workability when applied in an adhesive agent or a sealing agent. Therefore; as a technique generally used for decreasing the viscosity, mixing of a polymerizable monomer can be mentioned, but a polymerizable monomer that is compatible with a (meth)acrylic polymer and retains favorable curability is few, and the polymerizable monomer that can be used is limited. In a case where the compatibility is poor, a problem that cloudiness is caused at the time of curing and the deep portion is not cured is generated. Further, depending on the type of the polymerizable monomer, there is a problem that the cured product to be obtained has poor flexibility and the like.
In JP 2011-527722 W (corresponding to the specification of US 2011/068512 A), it has been disclosed that a composition having low viscosity, of which the cured product has rubber properties, can be obtained by selecting dimethyl acrylamide as a polymerizable monomer for an acrylate-terminated telechelic polyacrylate.